Interactive input systems that allow users to inject input (eg. digital ink, mouse events etc.) into an application program using an active pointer (eg. a pointer that emits light, sound or other signal), a passive pointer (eg. a finger, cylinder or other suitable object) or other suitable input device such as for example, a mouse or trackball, are known. These interactive input systems include but are not limited to: touch systems comprising touch panels employing analog resistive or machine vision technology to register pointer input such as those disclosed in U.S. Pat. Nos. 5,448,263; 6,141,000; 6,337,681; 6,747,636; 6,803,906; 7,232,986; 7,236,162; and 7,274,356 assigned to SMART Technologies ULC of Calgary, Alberta, Canada, assignee of the subject application, the entire contents of which are herein incorporated by reference; touch systems comprising touch panels employing electromagnetic, capacitive, acoustic or other technologies to register pointer input; tablet personal computers (PCs); laptop PCs; personal digital assistants (PDAs); and other similar devices.
Above-incorporated U.S. Pat. No. 6,803,906 to Morrison et al. discloses a touch system that employs machine vision to detect pointer interaction with a touch surface on which a computer-generated image is presented. A rectangular bezel or frame surrounds the touch surface and supports imaging devices in the form of digital cameras at its corners. The digital cameras have overlapping fields of view that encompass and look generally across the touch surface. The digital cameras acquire images looking across the touch surface from different vantages and generate image data. Image data acquired by the digital cameras is processed by on-board digital signal processors to determine if a pointer exists in the captured image data. When it is determined that a pointer exists in the captured image data, the digital signal processors convey pointer characteristic data to a master controller, which in turn processes the pointer characteristic data to determine the location of the pointer in (x,y) coordinates relative to the touch surface using triangulation. The pointer coordinates are conveyed to a computer executing one or more application programs. The computer uses the pointer coordinates to update the computer-generated image that is presented on the touch surface. Pointer contacts on the touch surface can therefore be recorded as writing or drawing or used to control execution of application programs executed by the computer.
Multi-touch interactive input systems that receive and process input from multiple pointers using machine vision are also known. One such type of multi-touch interactive input system exploits the well-known optical phenomenon of frustrated total internal reflection (FTIR). According to the general principles of FTIR, the total internal reflection (TIR) of radiation traveling through an optical waveguide is frustrated when an object such as a pointer touches the waveguide surface, due to a change in the index of refraction of the waveguide, causing some radiation to escape from the touch point. In a multi-touch interactive input system, the machine vision system captures images including the point(s) of escaped radiation, and processes the images to identify the position of the pointers on the waveguide surface based on the point(s) of escaped radiation for use as input to application programs.
One example of interactive input system based on FTIR is disclosed in United States Patent Application Publication No. 2008/0179507 to Han. Han discloses a multi-touch sensing display system 50 shown in FIG. 1, employing an optical waveguide 52, a light source 54, light absorbing surface 56 and an imaging sensor 57, such as a camera. Light emitted from light source 54 undergoes total internal reflection within optical waveguide 52. When an object, such as a finger F, is placed in contact with a contact surface of the optical waveguide, total internal reflection is frustrated thus causing some light to scatter from the optical waveguide. The contact will be detected by the imaging sensor. Moreover, a diffuser layer 58 is further disposed on the rear side of the waveguide for displaying images projected by a projector 59 arranged alongside the imaging sensor 57.
United States Patent Application Publication. No. 2008/00284925 to Han discloses an optical waveguide in the form of a clear acrylic sheet, directly against a side of which multiple high-power infrared LEDs (light emitting diodes) are placed. The infrared light emitted by the LEDs into the acrylic sheet is trapped between the upper or lower surfaces of the acrylic sheet due to total internal reflection. A diffuser display surface or a LCD panel is disposed alongside the non-contact side of the acrylic sheet with a small gap between the two in order to keep the diffuser from frustrating the total internal reflection. Imaging sensors mounted orthogonally relative to the waveguide or on the side of an optical wedge beneath the waveguide detects the light escaped from the waveguide. Multi-touch detections are achieved.
United States Patent Application Publication No. 2004/0252091 to Ma et al. discloses a multi-touch interactive input system. Light from two or more light sources mounted on the corner or midpoint of the edge of a touch panel are coupled into a waveguide by a prism to sustain transmission through the waveguide by total internal reflection. The transmitted light is detected by arrays of light detectors around the periphery of the waveguide opposite to each light source. Contacts of objects on the touch panel cause two or more intersecting light beams having known end points to be attenuated, enabling a processor to determine the position and size of the contacts.
United States Patent Application Publication No. 2009/0027357 to Morrison discloses a system of detecting contact on a display employing FTIR. The system includes a planar waveguide associated with a display and includes at least one edge facet and opposing surfaces. The system also includes one or more light emitting diodes such as LEDs coupled to the at least one edge facet for transmitting an optical signal into the waveguide such that the transmitted optical signal is totally internally reflected between the at least one edge facet and opposing surfaces. At least one optical sensing device, such as a camera, positioned substantially to face at least a portion of the edge facet, has a field of view of the entire top surface of the waveguide. Images of the top surface of the waveguide are analyzed to determine the location of contact on the display.
U.S. Provisional Patent Application No. 61/239,057 to McGibney et al., the content of which is incorporated herein by reference, discloses an interactive input system with improved signal-to noise ratio and image capture method. The interactive input system is shown in FIGS. 2A and 2B, and includes an optical waveguide 60 associated with a display having a top surface with a diffuser 62 on it for contact by an object, such as a finger F. The system also includes two light sources. Light from the first light source 64 is coupled into the optical waveguide and undergoes total internal reflection within the waveguide. Light from second light source 66 is directed towards another surface opposite to the top surface (the back surface). At least one imaging device, such as a camera 68, has a field of view looking at the back surface of the waveguide and captures image frames in a sequence with the first light source and the second light source being turned alternately on and off. In this way, processing of images in the sequence can be conducted in a manner that improves the signal-to-noise ratio of the system, so that pointer detected is improved. Like other interactive input systems, with the pointer(s) having been detected, the interaction with the touch surface can be recorded as handwriting or drawing to control execution of the application program, such as the images projected on the diffuser layer 62 by the projector 70.
United States Patent Application Publication No. 2009/0122020 to Eliasson et al. discloses a touch pad system including a radiation transmissive element. The transmissive element includes a first surface being adapted to be engaged by an object so as to reflect/scatter/emit radiation into the element, and a second surface opposite to the first surface. A detecting means is provided on either surface of the transmissive element. A modulation means is provided and adapted to prevent at least part of the reflected/scattered/emitted radiation by the object such that radiation from an object is detected by the detecting means after special modulation of the modulation means. Positions of contact on the surface of the transmissive element can be determined.
U.S. Pat. No. 7,442,914 to Eliasson et al. describes a method and a system for determining the position of a radiation emitter, which radiation emitter may be an actively radiation emitting stylus, pen, pointer, or the like or may be a passive, radiation scattering/reflecting/diffusing element, such as a pen, pointer, or a finger of an operator. Radiation from the emitter is reflected from its position toward the detector by a reflecting element providing multiple intensity spots on the detector thereby providing sufficient information for determining the position. From the output of the detector, the position of the radiation emitter is determined.
Although there are various configurations for an interactive input system to detect touch contact using FTIR technology, most of systems have detecting means such as a camera looking at the back surface of the touch screen, and they require a projector to project images. As a result, such systems are typically very large, are heavy, and are not considered portable.
It is an object of at least one aspect of the present invention to provide a novel interactive input system that can be constructed compactly.